The present invention generally relates to a remote control system and, more particularly, to a remote control system for remotely controlling devices such as appliances, entertainment equipment, and heating/cooling equipment.
Wireless remote controls for controlling appliances, entertainment equipment, heating/cooling equipment and even the firmness of a bed are well-known. In one implementation, a hand-held infrared remote control generates infrared signals based on user inputs. For example, in the case of a hand-held remote control for controlling a television, the user may press a POWER button on the remote control. A control circuit of the hand-held remote control processes this user input and generates an infrared signal by, for example, accessing a memory to retrieve a code corresponding to the user input and then using the retrieved code to generate and transmit the infrared signal. The television has an infrared receiver that receives the infrared signal. A control circuit of the television is responsive to the received infrared signal to xe2x80x9cpower onxe2x80x9d the television. Similar operations occur when the user presses buttons on the remote control for changing channels, increasing/decreasing volume, etc.
Manufacturers often provide remote controls for particular devices to consumers. A problem arises in that consumers can quickly accumulate a large number of different remote controls, each of which controls only one particular device. A solution to this problem is provided by so-called xe2x80x9cuniversalxe2x80x9d remote controls that are usable to control a number of different devices. For example, a single universal remote control may be used to control a television, a video recorder/player, and stereo equipment. Generally speaking, these universal remote controls include a memory that has a library of codes for different devices. The consumer configures the remote control so that codes in the memory that are appropriate to the particular makes and models of the devices owned by the consumer are accessed and used to generate the signals for controlling these devices.
To perform certain desirable operations, the control of various devices must be coordinated. For example, to record a television program, a set-top box must be tuned to a particular channel at (or slightly before) the program start time and a video recording device (e.g., a video cassette recorder) must be turned on at (or slightly before) the program start time, controlled to begin a recording operation, and controlled to end the recording operation at the program end time. In order to simplify this operation for users, some set-top boxes are provided with remote control circuitry for remotely controlling a video recording device. These set-top boxes may be provided with an interface that permits users to select future programs for recording. Such an interface is described, for example, in U.S. Pat. No. 5,479,268, the contents of which are incorporated herein. Using information about the future programs (e.g., start time, end time, channel), the set-top box tunes itself to the channel carrying the program at (or slightly before) the start time of a program selected for recording. The set-top box also generates remote control signals for turning on the video recording device and for initiating the recording operation. When the program ends, the set-top box generates remote control commands for ending the recording operation and for turning off the video recording device.
In some instances, the remote control circuitry of the set-top box comprises a controller (e.g., an 8-bit controller) that is separate from, but responsive to, a main microprocessor that controls the overall functionality of the set-top box. FIG. 1 shows an arrangement including a main microprocessor 8, controller 10, a memory 12, an input device 14, and light-emitting diodes (LEDs) 18. In response to instructions from main microprocessor 8 for switching on a video recording device, for example, controller 10 accesses appropriate codes from memory 12. These codes are used to control the on/off switching of LEDs 18 to thereby generate an infrared signal for switching on the video recording device. Input device 14 such as a keypad is operable by a user to input commands including, but not limited to, commands for the remote control of other devices via the remote control circuitry. Input device 14 may even be an infrared receiver for receiving user commands from a hand-held remote control. While this arrangement works quite effectively, the requirement of a controller that is separate from the main microprocessor tends increase the cost of the set-top box.
In other instances, the main microprocessor is itself configured to generate the infrared remote control signals. That is, the main microprocessor accesses appropriate codes from a memory, and uses the accessed codes to drive the LEDs. This arrangement also works quite effectively and does not require a separate controller for the remote control circuitry. However, it requires that the main microprocessor have processing power sufficient to perform remote control operations, while at the same time performing other set-top box functions such as memory accesses, video transfer, decryption, modem communications, and the like. Since the generation of infrared control signals involves a large number of interrupts to a microprocessor, the efficiency at which the microprocessor performs its other functions can be reduced, particularly if low-cost microprocessors having relatively low processing power are used.
In order to avoid these and other disadvantages of the prior art system described above, the remote control system described herein uses simple logic circuitry to drive the remote control transmitter. This logic circuitry is a very low cost alternative to using a separate controller dedicated to remote control operations. In addition, the logic circuitry is designed to minimize the interruptions to a microprocessor so that the microprocessor may efficiently perform its other functions.